Ms. Albarico Often, when real-world data is plotted, the result is a linear pattern. The general...
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Ms. Albarico 4.4 - Scatter Plots, Lines of Best Fit, & Correlation
Ms. Albarico Often, when real-world data is plotted, the result is a linear pattern. The general direction of the data can be seen, but the data points
Often, when real-world data is plotted, the result is a linear
pattern. The general direction of the data can be seen, but the
data points do not all fall on a line. This type of graph is a
scatter plot. A scatter plot is often used to investigate the
relationship (if one exists) between two sets of data. The data is
plotted on a graph such that one quantity is plotted on the x-axis
and one quantity is plotted on the y-axis. If the relationship does
exist between the two sets of data, it will be visible when the
data is plotted.
Slide 4
Example 1: The following graph represents the relationship
between the price of lobster per pound and the number of lobsters
sold.
Slide 5
From the graph, the connection between the cost of the lobster
and the number sold is obvious: as the price decreased the number
of lobsters sold increased.
Slide 6
From the graph, it is clearly seen that there is no
relationship between the number of lottery tickets sold and the
temperature of the surrounding environment.
Slide 7
Correlation refers to the relationship or connection between
two sets of data. The correlation between two sets of data can be
weak, strong, negative, or positive, or in some cases there can be
no correlation. The characteristics of the correlation between two
sets of data can be readily seen from the scatter plot. (Make sure
you run the Diagnostic ON first or the r wont be displayed.)
Slide 8
Correlation coefficient is a number that describes how well a
line models the data. The closer to 1 or -1 the coefficient, the
stronger the the correlation. A correlation that is positive means
that as one variable increases, the other variable increases,
resulting in a positive slope. A correlation that is negative means
that as one variable increases, the other decreases, resulting in a
negative slope.
Slide 9
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Slide 12
A line of best fit is drawn on a scatter plot so that it joins
as many points as possible and shows the general direction of the
data. Also called as trend line.
Slide 13
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Slide 15
Summary Point one point that best represents all the points in
a group of data. Its x-coordinate is the median of the x-values and
its y- coordinate is the median of the y-values.
Slide 16
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CYU # 8, 9, & 10 0n page 94. 17, 18, 19, 20, and 21 on
pages 197-198. Submit Inv. 5 next Friday!